CONFIG: adjust settings for solaris and darwin

solaris:
  - rename WM_ARCH from SunOS to solaris64 for consistency with wmake/rules
  - drop non-64 solaris from wmake/rules
  - remove automatic selection of FJMPI. This should be done in the bashrc
    or prefs.sh file instead.
  - remove old (likely inaccurate) exported flags, rely on wmake -show-xyz
    or user config instead

darwin:
  - remove '-Ddarwin' from the exported WM_CFLAGS, WM_CXXFLAGS.
    Not used elsewhere (ThirdParty)